A group of topological index ND data based on distance matrix and branch vertex of atoms in a molecule was put forward by colouring atoms in the molecular graph with equilibrium electronegativity, which appears unique to the molecular structures and has excellent structural selectivity. The results show that the additive property P of alkanes could be described as follows: P＝aND₁＋bND₂＋cND₃＋d by study on the additive property of alkanes and their homologous regularity using topological index ND, where a, b, c and d are conferred as constants. The calculated values conform very much to the experimental ones of gas enthalpy (Δ_fH^ө_m), entropy (Δ_fS^ө_m), Gibbs energy (Δ_fG^ө_m) of 85 alkanes and molar volume (V_m), molar refraction (R_m) of 67 alkanes from literatures using the formula above.

Key words: alkane, atomic equilibrium electronegativity, topological index ND, additive property, homologous regularity